Similar to the Writer API, this can only be extended for 3 months. See
similar questions on progress below, thanks.
On 10/28/25 11:40 a.m., Deepti Bogadi wrote:
Gentle reminder to review the Intent to Extend Experimentation for the
Rewriter API. Let me know if you have any questions.
Thanks,
Deepti
On Wed, Oct 22, 2025 at 11:18 AM Deepti Bogadi <[email protected]>
wrote:
Contact emails
[email protected], [email protected],[email protected]
Explainer
https://github.com/explainers-by-googlers/writing-assistance-apis/blob/main/README.md
<https://github.com/explainers-by-googlers/writing-assistance-apis/blob/main/README.md>
Specification
https://webmachinelearning.github.io/writing-assistance-apis/#rewriter-api
<https://webmachinelearning.github.io/writing-assistance-apis/#rewriter-api>
Summary
The Rewriter API transforms and rephrases input text in requested
ways, backed by an on-device AI language model. Developers may use
this API to remove redundancies within a text in order to fit into
a word limit, rephrase messages to suit the intended audience or
to be more constructive if a message is found to use toxic
language, rephrasing a post or article to use simpler words and
concepts and more. An enterprise policy
(GenAILocalFoundationalModelSettings) is available to disable the
underlying model downloading which will render the API unavailable.
Blink component
Blink > AI > Writing Assistance
<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%20%3E%20AI%20%3E%20Writing%20Assistance%22>
Web Feature ID
No information provided
TAG review
https://github.com/w3ctag/design-reviews/issues/991
<https://github.com/w3ctag/design-reviews/issues/991>
TAG review status
Pending
Origin Trial Name
Rewriter API
Chromium Trial Name
AIRewriterAPI
Origin Trial documentation link
https://github.com/webmachinelearning/writing-assistance-apis/blob/main/README.md#rewriter-api
WebFeature UseCounter name
Rewriter_Create
Risks
Interoperability and Compatibility
This feature has definite interoperability and compatibility
risks, due to the likelihood that different implementations will
use different language models, prompts, and fine-tunings, and even
within a single implementation such as Chrome, these pieces will
likely change over time. Additionally, not all browsers and
operating systems will have a built-in language model to expose,
and not all devices will be powerful enough to run one
effectively. We are taking a variety of steps to attempt to
mitigate these risks. For example, the specification is designed
to allow the API to be backed by a cloud-based language model.
This approach could extend the functionality to a wider range of
devices and users. The API is designed to abstract away the
specifics of the underlying language model, including prompts and
fine-tuning. This prevents developers from relying on specific
outputs, ensuring they receive rewritten text rather than
structured data that might vary across implementations. Finally,
the API surface is designed with many clear points of failure,
that encourage the developer to probe for capabilities ahead of
time and fall back to other techniques if a capability is not
available. Nevertheless, interoperability and compatibility risk
remains high for these sorts of APIs, and we'll be closely
monitoring it during the experiment period.
Gecko: Negative
(https://github.com/mozilla/standards-positions/issues/1067
<https://github.com/mozilla/standards-positions/issues/1067>)
WebKit: No signal
(https://github.com/WebKit/standards-positions/issues/393
<https://github.com/WebKit/standards-positions/issues/393>)
Web developers: Mixed signals
(https://github.com/WICG/proposals/issues/163
<https://github.com/WICG/proposals/issues/163>) Prototyping with
partners behind a flag revealed enthusiasm and many prototypes
built, from which we drew the discussion of potential use cases
[1]. Feedback on the WICG thread was more mixed. Some themes we
saw include: asking for more capabilities (e.g. full prompting of
a language model instead of higher-level APIs (our response at
[2]); multi-modal support); desire to make sure the API actually
works robustly in many real-world use cases; removal of any
safety/ethical safeguards; and confusion about client-side vs.
cloud APIs. [1]:
https://github.com/WICG/writing-assistance-apis/blob/main/README.md#summarizer-api
<https://github.com/WICG/writing-assistance-apis/blob/main/README.md#summarizer-api>[2]:
https://github.com/WICG/writing-assistance-apis/blob/main/README.md#directly-exposing-a-prompt-api
<https://github.com/WICG/writing-assistance-apis/blob/main/README.md#directly-exposing-a-prompt-api>
Other signals:
Activation
This feature would definitely benefit from having polyfills,
backed by any of: cloud services, lazily-loaded client-side models
using WebGPU, or the web developer's own server. We anticipate
seeing an ecosystem of such polyfills grow as more developers
experiment with this API.
WebView application risks
Does this intent deprecate or change behavior of existing APIs,
such that it has potentially high risk for Android WebView-based
applications?
No information provided
Goals for experimentation
Although developers have prototyped using the behind-a-flag
implementation and given good feedback, several partners are
interested in testing out the API with real users. We're looking
forward to getting feedback from such testing, especially with
regards to output quality, multilingual support, and what types of
input data are handled well vs. poorly. We also want to understand
whether we've found the right set of options to offer to control
the output, and whether the resulting output reflects those
controls to the extent that developers expect.
Reason this experiment is being extended
Rewriter API suffers from perceived quality issues and a critical
language support disconnect. These APIs are currently not
production-ready for many use cases, particularly those outside of
English. In addition, we are also seeing low adoption in the OT
phase for this API. Hence, we are requesting the extension of the
trial to give us time to collect more feedback from our partners
and make the API more robust and resilient.
Can you please comment on progress in these areas, per
https://www.chromium.org/blink/launching-features/#origin-trials?
Draft spec (early draft is ok, but must be spec-like and associated with
the appropriate standardization venue, or WICG)
TAG review (see exceptions)
signals requests
Outreach for feedback from the spec community
WPT tests
Ongoing technical constraints
As discussed above, not all devices are capable of running the
language models required to implement this API. The availability()
function allows developers to feature-detect whether the current
device can support the API.
Debuggability
It is possible that giving DevTools more insight into the
nondeterministic states of the model, e.g. random seeds, could
help with debugging. See related discussion at
https://github.com/explainers-by-googlers/prompt-api/issues/9
<https://github.com/explainers-by-googlers/prompt-api/issues/9>.
Will this feature be supported on all six Blink platforms
(Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?
No
Not all platforms will come with a language model. In particular,
in the initial stages we are focusing on Windows, Mac, and Linux.
Is this feature fully tested by web-platform-tests
<https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?
No
The API surface is reasonably well tested with mocked models, but
production model downloading and non-deterministic outputs are not
fully tested at the web-platform-tests layer. The explainer
discusses this in
https://github.com/WICG/writing-assistance-apis/blob/main/README.md#specifications-and-tests
<https://github.com/WICG/writing-assistance-apis/blob/main/README.md#specifications-and-tests>.
DevTrial instructions
https://docs.google.com/document/d/1v6-fOC13zS3S-bOLuqIRbzgmia_aPGJl-wzOx4ItSVE/edit?usp=sharing
<https://docs.google.com/document/d/1v6-fOC13zS3S-bOLuqIRbzgmia_aPGJl-wzOx4ItSVE/edit?usp=sharing>
Flag name on about://flags
rewriter-api-for-gemini-nano
Finch feature name
AIRewriterAPI
Requires code in //chrome?
True
Tracking bug
https://issues.chromium.org/issues/358214322
<https://issues.chromium.org/issues/358214322>
Launch bug
https://launch.corp.google.com/launch/4396842
<https://launch.corp.google.com/launch/4396842>
Non-OSS dependencies
Does the feature depend on any code or APIs outside the Chromium
open source repository and its open-source dependencies to function?
Yes: this feature depends on a language model, which is bridged to
the open-source parts of the implementation via the interfaces in
//services/on_device_model.
Estimated milestones
Origin trial desktop first
137
Origin trial desktop last
142
Origin trial extension 1 end milestone
148
DevTrial on desktop
129
Anticipated spec changes
Open questions about a feature may be a source of future web
compat or interop issues. Please list open issues (e.g. links to
known github issues in the project for the feature specification)
whose resolution may introduce web compat/interop risk (e.g.,
changing to naming or structure of the API in a
non-backward-compatible way).
At this point all known proposed changes have been incorporated
into the specification and implementation.
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5112320150470656?gate=5133588907556864
<https://chromestatus.com/feature/5112320150470656?gate=5133588907556864>
Links to previous Intent discussions
Intent to Prototype:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra9Jhe7o59mX5tJPD%3DcZQb2oL3mNi-T57wA86fPXn55OPw%40mail.gmail.com
<https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra9Jhe7o59mX5tJPD%3DcZQb2oL3mNi-T57wA86fPXn55OPw%40mail.gmail.com>
Intent to Experiment:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra8dnNHXKM26MvQxZ6LBE16PUbvH6-GH5B3Z2WDv4uH0WQ%40mail.gmail.com
<https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra8dnNHXKM26MvQxZ6LBE16PUbvH6-GH5B3Z2WDv4uH0WQ%40mail.gmail.com>
This intent message was generated by Chrome Platform Status
<https://chromestatus.com/>.
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